This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Botulinum neurotoxins are the virulence factors that cause the disease botulism in humans and animals. They are one of the six most dangerous potential bioterrorism agents. Due to their ability to modulate neuronal activity, they are also used to treat a variety of medical conditions. Therefore, there is a great need to learn the molecular mechanisms for the mode of action of these toxins. This project seeks to identify the cellular receptors for botulinum neurotoxins and to understand how botulinum neurotoxins target and enter neuronal cells.